The Fossil Insects of the Quercy Region 127
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The Fossil Insects of the Quercy Region 127 Entomologie heute 28 (2016): 127-142 The Fossil Insects of the Quercy Region: A Historical Review Die fossilen Insekten der Quercy Region: eine historische Übersicht ACHIM H. SCHWERMANN, MICHAEL WUTTKE, TOMY DOS SANTOS ROLO, MICHAEL S. CATERINO, GÜNTER BECHLY, HEIKO SCHMIED, TILO BAUMBACH & THOMAS VAN DE KAMP Summary: At the end of the 19th century, numerous mineralized insects from the Paleogene were dis- covered during phosphorite mining in the former province of Quercy in France. Despite their unusual three-dimensional preservation, the Quercy insects received only minor attention from the scientifi c community. During the time of mining, the only detailed study on the subject was provided in 1890 by KARL FLACH, who described two carrion beetle species. More than fi ve decades later, the Swiss entomologist EDUARD HANDSCHIN published the fi rst and hitherto only comprehensive study on the Quercy insects. Unfortunately, his detailed work did not draw the attention of paleoentomologists to these fascinating fossils. More than 70 years after HANDSCHIN’s study, recent examinations provided fascinating new insights into this almost forgotten fossil type. While the descriptions by the early researchers were largely restricted to the external shape of the specimens, X-ray microtomography now permits detailed non-destructive examination of their internal composition. The latest study revealed extraordinarily well-preserved ana- tomical characters in a fossil hister beetle (Histeridae: Onthophilus intermedius Handschin, 1944), which was largely hidden inside a stony matrix. This fi nding suggests that the Quercy specimens constitute a rich but yet largely unexploited source for anatomical data of fossil insects. Keywords: Paleogene, phosphatization, mineralization, FRANÇOIS GERVAIS, HENRI FILHOL, ARMAND THÉVENIN, KARL FLACH, EDUARD HANDSCHIN Zusammenfassung: Gegen Ende des 19. Jahrhunderts wurden während des Phosphorit-Abbaus in der ehemaligen Provinz Quercy in Frankreich zahlreiche mineralisierte Insekten aus dem Paläogen gefunden. Trotz ihrer ungewöhnlichen dreidimensionalen Erhaltung haben die Quercy-Insekten jedoch nur wenig Beachtung in der wissenschaftlichen Welt erfahren. KARL FLACH veröffentlichte 1890 die einzige während der Abbauphase entstandene Studie zu dem Thema, in der er zwei Aaskäferarten beschreibt. Mehr als fünf Jahrzehnte später publizierte der Schweizer Entomologe EDUARD HANDSCHIN die erste und bisher einzige umfassende Studie über die Quercy-Insekten. Unglücklicherweise hat auch seine detaillierte Arbeit nicht die Beachtung der Paläoentomologen für diese faszinierenden Fossilien wecken können. Mehr als 70 Jahre nach HANDSCHINs Studie ermöglichten aktuelle Untersuchungen nun faszinierende neue Einsichten in einen fast vergessenen Fossilientyp. Während die Untersuchun- gen der ersten Bearbeiter weitgehend auf die äußere Form der Stücke beschränkt waren, erlaubt die Röntgen-Mikrotomographie heutzutage eine zerstörungsfreie Untersuchung ihres internen Aufbaus. Die jüngste Arbeit offenbarte außergewöhnlich umfassend überlieferte anatomische Merkmale eines Stutzkäfers (Histeridae: Onthophilus intermedius Handschin, 1944), der größtenteils im Gestein verborgen ist. Dieses Ergebnis verdeutlicht, dass die Quercy-Insekten eine reichhaltige und bislang weitgehend unerschlossene Quelle für anatomische Informationen fossiler Insekten darstellen. Schlüsselwörter: Paläogen, Phosphatisierung, Mineralisation, FRANÇOIS GERVAIS, HENRI FILHOL, ARMAND THÉVENIN, KARL FLACH, EDUARD HANDSCHIN Entomologie heute 28 (2016) 128 ACHIM H. SCHWERMANN et al. 1. Introduction phatized arthropods – most of them insects – were found alongside the vertebrate fossils. Arthropod fossils occur in many varieties, A fascinating feature of the Quercy arthropods e.g. as compressions and impressions, casts, is their three-dimensional preservation, while embeddings, or inclusions in amber (GRI- most fossil arthropods – with the exception MALDI et al. 1994; MARTÍNEZ-DELCLÒS et al. of amber inclusions – are compressed to two- 2004; GRIMALDI & ENGEL 2005; PENNEY & dimensional objects. However, despite their JEPSON 2014). While amber inclusions are unusual properties, the insects of the Quercy most famous for their exquisite preservation received only minor attention in the scientifi c of three-dimensional shape, sometimes even community. preserving soft tissues (PERREAU & TAFFO- Here we highlight the scientific history REAU 2011; VAN DE KAMP et al. 2014), 3D of the Quercy insects, comment on their arthropod fossils are also known from con- fossilization and demonstrate how state-of- cretions, hollow casts, encapsulations and the-art digital imaging techniques facilitate mineral replications. In mineralized fossils, fascinating new insights into a fossil type that organic tissues are replaced by minerals like was largely neglected by paleoentomologists calcite (MCCOBB et al. 1998), silica (MILLER for more than a century. & LUBKIN 2001), pyrite (GRIMALDI & ENGEL 2005), or phosphate (DUNCAN & BRIGGS 2. The history of the Quercy locality 1996; HELLMUND & HELLMUND 1996; WA- LOSZEK 2003). These fossils are known from Phosphate was discovered to be a potent many localities and geological ages, but while fertilizer by JUSTUS VON LIEBIG in 1840, there are several examples of mineralized triggering the search and mining of natural arthropod fossils from marine deposits (e.g. accumulations of phosphorite in the second MA et al. 2013; CONG et al. 2014; EDGECOMBE half of 19th century. After phosphorite was et al. 2015; SIVETER et al. 2007, 2013, 2014), found in the fi ssure fi llings of Quercy in mineralization within subaerial conditions 1865 (THÉVENIN 1903), intensive mining are generally less known. took place from 1870 until the end of that At the end of the 19th century nu mer ous fossils century (FILHOL 1876b; HANDSCHIN 1944; were discovered in the former Quercy pro- Fig. 1A). The fi ssure fi llings originate mainly vince in southwestern France. Whereas most from the Paleogene (LEGENDRE et al. 1997), vertebrates from that locality were represented when Mesozoic bedrocks of the region of merely by bones and teeth, a smaller number the Quercy (Jurassic limestones and marls, of body fossils of mineralized – or more pre- Cretaceous calcareous sandstones and reefal cisely phosphatized – frogs, salamanders, and clayey limestones) were subject to erosion snakes were described (FILHOL 1876a; LALOY and karstifi cation. The environment was et al. 2013; TISSIER et al. 2015). Multiple phos- like a tropical rainforest, crossed by rivers Fig. 1: The locality and related researchers. A Phosphorite mine in the Quercy region (photograph taken from THÉVENIN 1903). B FRANÇOIS LOUIS PAUL GERVAIS (1816-1879); public domain picture originally published in “Popular Science Monthly”, August 1887. C PIERRE ANTOINE HENRI FILHOl (1843-1902); source unknown; restored by DIDIER DESCOUENS, Muséum de Toulouse. D EDUARD HANDSCHIN (1894-1962); courtesy of W. ETTER, Naturhistorisches Museum Basel. Abb. 1: Der Fundort und seine Bearbeiter. A Phosphoritmine im Quercy (Foto aus THÉVENIN 1903). B FRANÇOIS LOUIS PAUL GERVAIS (1816-1879); gemeinfreies Bild, ursprünglich gedruckt in „Popular Science Monthly“, August 1887. C PIERRE ANTOINE HENRI FILHOL (1843-1902); Quelle unbekannt; restauriert von Didier Descouens, Muséum de Toulouse. D Eduard Handschin (1894- 1962); freundlicherweise zur Verfügung gestellt von W. ETTER, Naturhistorisches Museum Basel. The Fossil Insects of the Quercy Region 129 Entomologie heute 28 (2016) 130 ACHIM H. SCHWERMANN et al. coming down from the Massif Central. Wa- In 1890 the German entomologist KARL ter, enriched with carbon dioxide, penetrated L. FLACH (1856-1920) documented four through fractures within the rocks, and dis- specimens from Caylus1: an ootheca of a solved and dug cavities into the subsurface cockroach species (genus Blatta), a larva of of the Jurassic limestones (BRUXELLES et al. a cicada, and two carrion beetles (Silphidae), 2008). The tropical erosion at the surface which he illustrated in detail (FLACH 1890; led to an intense lateritization of the Jurassic Fig. 2). He compared both beetle specimens and Cretaceous sediments, which partly were with modern taxa, found most similarities accumulated as limey clays and sands, rich with the genera Necrodes and Ptomascopus, and in iron and phosphate (GÉZE 1938, 1949), described them as new species (Palaeosilpha within the karstic cavities. Additionally those Fraasii [sic!] & Ptomascopus aveyronensis). Flach cavities acted as traps for vertebrate remains assumed a slow fossilization process invol- like teeth and bones and invertebrates. ving adipocere, and hypothesized vertebrate Unfortunately, little attention was paid to bones as the primary phosphate source, the stratigraphic differences between the which triggered the mineralization: multiple localities during the excavations in “Die Umwandlung scheint eine sehr langsame gewe- the 19th century. As known nowadays, they sen zu sein und nimmt man an, daſs der Versteine- cover mainly the time of the Middle and rung ein Zustand der Leichenwachsmetamorphose Late Eocene up to the beginning of the (Adipocire-Bildung) vorausgegangen sei. Die später late Oligocene. But also fossils from the sich einlagernden Phosphorsalze entstammen vorzüg- early Eocene (about 50 Ma) up to the lower lich Thier- bezw. Knochenresten in der Umgebung Miocene (about 20 Ma) are known (SIGÉ et und es ist nicht undenkbar, daſs die beiden Käfer al. 1991; LEGENDRE